This is a method and apparatus for coating pipe with foamed insulation, a method for marking lengths of pipe coated with foam, and a method and apparatus for handling pipe coated with foamed insulation.
Utilization of insulating jackets around pipe has long been employed in oil recovery and oil transportation. It is often necessary to heat the oil to be able to remove it from the ground and also to lower the viscosity for transportation through pipelines. In most geographical areas the temperature of the heated liquid can be maintained at the desired level only by insulating the pipe through which the oil flows. Other uses of insulated pipe include natural gas recovery, water, steam and sewer pipes.
Many prior art techniques have been developed for enveloping a pipeline in a layer of foamed insulation. Some prior art techniques are characterized by mold forming of the foamed insulating jacket although such a process is limited as to production capabilities and is accordingly expensive. Another prior art technique which has been utilized is to extrude the foamable liquid inside of an enveloping jacket as the pipe lays in place in a ditch along the pipeline right of way. Machines have been developed for lifting the pipeline out of the ditch a sufficient distance to allow extrusion of the foamed insulating jacket and then replacement of the pipe into the ditch. Such an "over the ditch" process does not provide for optimum control over cell structure and compressive strength of the end product.
Another prior art technique which has been attempted is to spray a foamable liquid onto the pipe as it is advanced longitudinally and rotated about its longitudinal axis. Such spray foaming techniques have heretofore suffered from an inability to accurately control the thickness of the foamed insulation as well as the cell structure and compressive strength of the final product.